Hydraulic actuator system



July 5, 1938. E. J. SVENSON 2,122,443

HYDRAULIC ACTUATOR SYSTEM Filed July 25, 1931 2 Sheets-Sheet l b 90 I I/Patented- July 5, 1938 UNITED STATES PATENT OFFICE 21 Claims.

My invention relates generally to improvements in hydraulic systems ofcontrol, and particularly to improvements in systems whereby the speedof travel of a hydraulic actuator may be effectively controlled.

It has been the common practice, in designing machines for propellingmachine tools and the like, to provide means for moving said tools atvarious speeds. My present invention relates particularly to hydraulicdevices for propelling ma chine tools and the like. Fluid pumps, such ashigh displacement gear pumps, are in some instances employed to effectthe rapid movement or traverse of a hydraulic actuator piston which iscoupled with a machine tool carriage. These pumps are sometimescontinuously driven at a constant maximum rate, and experience has shownthat, as a result of this continuous operation, the fluid in the systembecomes heated. Some of the conventional fluid types of circuits withwhich I am familiar are so arranged that the rapid traverse pump mustcontinuously function at nearly its maximum rate in order to take careof leakage within high pressure pumps which are associated with saidcircuits for the purpose of supplying fluid under relatively highpressure to the actuator piston.

It is one of the primary objects of my present invention toavoid theabove mentioned temperature rise in the fluid medium by coupling a rapidtraverse fluid pump with a circuit containing an actuator cylinder andpiston, in such a manner that the pump displacement may be varied inaccordance with the requirements of the circuit. To this end I proposeto provide means whereby the displacement of the rapid traverse pump maybe maintained at a minimum when the circuit conditions are such as notto require a greater displacement, and whereby the displacement ofcreased when the circuit conditions are such as to require it.

Another object of my invention is to provide, in combination with acircuit employing a high pressure pump for feeding purposes and a lowerpressure pump for rapid traverse purposes, means whereby thedisplacement of the rapid traverse pump may be varied from apredetermined minimum to a predetermined maximum in accordance with theoperating requirements of the circuit, which includes both of saidpumps.

Still another object is to provide, in combination with circuits of thetype in which one of the above mentioned pumps may operate forpropelling purposes independently of the other,

the pump may be manually or automatically in means for causing the rapidtraverse pump to operate at a minimum displacement during the operativefunctioning of the high pressure pump and to operate at increaseddisplacement when the circuit is to be conditioned for rapid traverse 5purposes.

More specifically, my invention contemplates the provision of meanswhich may be operated manually or which may be operated in response tothe actuation of a machine element propelled 10 by an actuator piston,to thereby effect a variation in displacement of the rapid traverse pumpeither by varying the speed thereof or by controlling the passage offluid therethrough without affecting the rotative speed of the pump.

Still another object of my invention is to provide a control means forrapid traverse pumps, as above set forth, which will function inresponse to pressure conditions within the fluid circuit coupledtherewith.

The foregoing and numerous other objects and advantages will be moreapparent from the following detailed description when considered inconnection with the accompanying drawings, wherein Figure 1 is adiagrammatic representation of a fluid circuit which is arranged inaccordance with the teachings of my present invention;

Figure 2 is a transverse sectional view of the main control valve, saidview being taken sub- 30 stantially along the line 2-2 of Figure 1;

Figure 3 is a fragmentary diagrammatic representation of a modifiedfluid circuit to disclose the manner in which the displacement of therapidtraverse pump may be varied without affecting 35 the speed thereof;

Figure 4 is a fragmentary sectional view disclosing the operativeconnection between the main control valve and the hydraulic actuator;and

Figure 5 is a transverse sectional view taken longitudinally of the dogcarrying slide, said view being taken substantially along the line 5-5of Figure 4.

Referring to the drawings more in detail where in like numerals havebeen employed to designate similar parts throughout the various figures,it will be seen that for the purpose of illustrating one practicalembodiment of the invention, I have 50 disclosed-1n a somewhat.schematic manner certain elements of a. material working apparatus, suchas a lathe of the type'disclosed in my copendlng application, Serial No.481,742, filed September 13, 1930, which has since matured into 55Patent No. 2,078,696, and I have indicated these elements generally bythe numeral I0, Figure 1. These elements include a suitable source ofpower supply, such as an electric motor I2, which is coupled through themedium of a chain I4 with an element I6 of a clutch mechanism I8. Acompanion clutch member 20 is keyed to a shaft 22 and is adapted toshift toward and away from the member I6. When the clutch member 201soperatively associated with the member I6, power is transmitted to theshaft 22, and this shaft is coupled by suitable gearing with a spindle24.

- This spindle 24 may be of any conventional type for supporting a workpiece or cutter and is coupled by means of a chain 26 with a highpressure plunger pump 28. Thus, when the drive shaft 22 is rotated, thespindle 24 and high pressure plunger pump 28 also function.

To control the shifting of the clutch member 20 I provide a fluidoperated mechanism 30, which includes a cylinder 32 and a piston 34therein. One end of the piston 34 is coupled with an arm 36 through theagency of a piston rod 38, and this arm is connected with a yoke 40,which serves as the actuating means for the clutch member 20. When thepiston 34 occupies the position shown in Figure 1, the clutch members I6and 20 are disengaged, and when the piston is shifted to the left, thesemembers operatively engage each other. The shifting of the clutchactuator piston 34 is controlled by the fluid in a circuit described.

This circuit includes the plunger pump 28 and a hydraulic actuator 42including a cylinder 44, the opposite ends of which are connected bymeans of pipe lines 46 and 48. with the intake and discharge sides ofthe plunger pump 28. In the disclosed embodiment the pipe line 46connects the intake side of the pump 28 with the right side of thecylinder 44, and the pipe line 48 connects the discharge side of thepump'with the left end of the actuator cylinder. Opposite extremities ofthe cylinder 44 are also connected by pipe lines 50 and 52 with a valvedesignated generally by the numeral 54. This valve is similar to thevalve disclosed in my above mentioned co-pending application, now PatentNo. 2,078,696, and therefore a detailed disclosure thereof is notessential to a full understanding of my present invention.

. A suitable fluid reservoir 56 is provided which communicates with theintake side of a gear pump 58through the agency of a pipe line 60, andfluid from the discharge side of the pump 58 communicates with theintake port 62 of the valve 54 by means of a pipe line 64, Figure 1. Thevalve 54 includes a cylindrical casing 66 and a valve member 68reciprocable therein. When the valve member 68 occupies the positionshown in Figure 1, fluid from the discharge side of the highdisplacement low pressure gear pump 58 is 1 directed through the intakeport 62 of the valve,

. say, the fluid pressure at the opposite extremities of the valvemember acts with substantially equal force, thereby preventing theinadvertent shifting of said valve member. Fluid from the passageway 18also communicates with a valve about to bev ically in Figure 1.

port which connects with a pipe line 82. This pipe line communicateswith a restricted oriflce 84 provided at the upper portion of thereservoir 56. By means of this fixed restricted orifice a predeterminedback pressure is set up within the fluid to maintain the desired fluidpressure within the system.

Assume that the valve member 68 is suddenly shifted to the left, eithermanually or automatically. This will establish communication between theintake port 62 of the valve and port 86 through a lateral passage 88provided in the valve member 68. The radial ports 10 will be closed,thereby preventing fluid under low pressure from' the gear pump to enterthe end chamber. I2. This fluid passes outwardly through the valve port86, through the pipe line 52, and enters the left end of the actuatorcylinder 44, thereby causing an actuator piston 90 to be urged totheright. This piston 90 may be connected with any shiftable machineelement such as a machine tool carriage or the like (not shown).Contemporaneously with the delivery of fluid to the left end of thecylinder 44, fluid under the same pressure is delivered to the right endof the cylinder 32 through a pipe line'92, thereby causing the piston 34to be urged to the left so as to operatively engage the clutch member 20with its companion member I6. Fluid from the opposite side of thecylinder 32 passes outwardly through a pipe line 94, which connects withthe return pipe line 50. This pipe line 50 connects with a valve port 96which at this instant communicates with the valve port 80 and the returnpipe line 82 through the agency of a valve passage 98.

Attention is now directed to a hydraulic ac tuator designated generallyby the numeral I00, which includes a cylinder I02 and an actuator pistonI04 reciprocable therein. A piston rod I06 carries a pair of spaced dogsI08 and H0. Positioned in the line of travel of these dogs are companionpilot switches H2 and H4 respectively. These switches may be of anyconventional design and are electrically coupled with a magneticcontactor II6, which is indicated diagrammat- This magnetic contactor II6 connects with the external source of power supply on one side andwith a two-speed motor II8 on the other side. When the valve member 68occupies the position shown in Figure 1, the motor II8 operates at itsslower speed say, for example, 450 R. P. M. This motor drives the gearpump 58. Thus when the pump 58 is not needed for rapid traversepurposes, that is, for the purpose of propelling the actuator piston 90at.a rapid rate, said pump operates at a relatively slow speed, therebypreventing increases in the temperature of the fluid medium whichnormally take place when conventional pumps are operated at a'high speedover a considerable period of time. When the valve member 68 is shiftedto the left in the manner described above, the increase in fluidpressure which occurs as a result of the delivery of said fluid to theleft end of the cylinder 44 causes the actuator piston I04 to be shiftedto the right. The cylinder I02 in which the piston I04 reciprocates isconnected to the intake port 62 of the valve 54 by a line I 20 and isconnected with the end chamber 12 by a line I2I. This causes the dogsI08 and H0 to depress buttons II2a and H41: of the pilot switches H2 andI I4 respectively. One of these switches may be of the conventionalnormally open type and the other of the conventional normally closedtype. Thus, by actuating these pilot switches, the magnetic contactor isenergized so as to cause the speed of .themotor II8 to be materiallyincreased. This increase in speed causes a corresponding increase in thespeed of the pump 58, thereby effecting increased fluid displacement tothe left end of the cylinder 44. This causes the piston 90 to be urgedat a rapid rate within the cylinder 44.

When the piston 90 hastraveled at a rapid rate a predetermined distanceto the right, the valve member 68 may be manually or automaticallyshifted to the neutral position shown in Fi ure 1. In this position thegear pump 58 is cut off from the cylinder 44, and the plunger pump 28continues to function in a closed circuit containing the pipe lines 46and 48 and the actuator 42 to propel the piston 90 at a feeding ratetothe right. Instantaneously upon the shifting of the valve to thisneutral position, the actuator piston I04 is shifted to the left. Thiswill be apparent from the factthat the piston area acted upon at theright end of the piston I04 is greater than the'area at the left due tothe presence of the piston rod I06. Thus, immediately upon shifting themain control valve 68 to its neutral position, the piston I04automatically shifts to the left, thereby causing the switches H2 and H4to condition the magnetic contactor II6 so as to reduce the speed of themotor 8'. The motor and consequently the gear pump 58 continue tooperate at the low speed during the operative functioning of the highpressure pump 28.

In order to more clearly set forth the arrangement just described, wecall attention to the fact that the discharge from the pump 58 when itis running at slow speed, flows through the following passages: Theintake port 62, the radial ports I in the valve member 68, thelongitudinal passage I4 in said valve member, the valve chamber I2, thepassageway I8, valve passage 98, valve port 80, and pipe line 82, whichconnects with the restricted orifice 84. Under these conditions therestricted orifice 84 causes the required amount of back pressure to bebuilt up within the system. However, with the pump 58 operating at slowspeed, the volumetric delivery thereof through the pipe line 82 isaccommodated by the restricted orifice 84 without necessitating theopening of the valve I3I.

A coiled spring I23 may be interposed between the right end of thepiston I04 and the inner surface of the cylinder wall, as clearly shownin Figure 1, if it is deemed necessary. For example, if the orifice 84were such as not to restrict the flow of fluid sufilciently to build upany appreciable pressure in the valve chamber I2 during .valve I24 tothe left. The movement of this valve to the left immediately establishescommunication between the right cylinder chamber 16 and the reservoir 56through longitudinal passages I26, a valve port I28, and a pipe lineI30. In this manner the pressure of the fluid through the chamber I6 isdecreased due to the fact that said fluid'may'flow unrestrictedly backinto the reservoir 58. This causes the unbalancing of the valve member68 within the casing 66 and results in the sudden shifting of said valvemember from its neutral position shown in Figure 1 to its extreme rightposition. In other words, by referring to Figures 1 and 3, it will beapparent that, upon movement of the valve I24 to the left, the end ofpassage 18 connected to the chamber I6 will be cut off at the same timethat valve port I28 is opened. Thus the valve 68 will be moved to theright by the pressure of fluid, because the pressure in chamber 12 willbe greater than in chamber I6. This is due to the fact that at thisinstant chamber I6 is out of communication with the passage I8 and infree communication with the reservoir 56 through passages I26 andconduit I30, the restriction at 84 causing a greater pressure in chamberI2. In this shifted position a reversal in fluid flow .within thecircuit takes place so that fluid from the pump 58 flows through theintake port 62 and then through the pipe line 50 into the right end ofthe cylinder 44, and fluid from the left end of said cylinder flowsthrough the pipe line 52 and into the left valve chamber I2. Fluidpressure in the pipe line 94 causes the piston 34 to be shifted to theright, thereby arresting the rotation of the spindle 24 and theactuation of the high pressure pump 28. contemporaneously with theshifting of the valve member 68, the piston I04 is again urged to theright so as to cause the motor H8 and consequently the gear pump 58 toincrease in speed. In this manner the piston 90 is driven at rapidtraverse to the left and the plunger pump 28 remains functionallyinoperative. When the piston reaches its starting position, the valve 68may be manually or automatically shifted to its neutral position,thereby causing the speed of the gear pump to be reduced andconditioning the circuit for a subsequent cycle of operation similar tothat just described.

Attention is directed to a. spring valve I3I which connects with thepipe 82, as clearly shown in Figure 1. This spring or relief Valve isadapted to open when sufficient pressure is exerted thereon, and thispressure is established within the pipe line or channel 82 only duringthe operative functioning of the pump 58, or, in other words. only whenthe piston 90 is being shifted at a rapid rate. ,During the operativefunctioning of the plunger pump 28 the pressure within the channel orpipe line 82 is not sufficient to open the relief valve I3I. In otherwords, I provide a low pressure circuit which is subjected to variationin pressures. Thus during the operative functioning of the gear pump 58for propelling the piston 90 at a rapid rate, the pressure is greaterthan when this pump 58 idles and the plunger pump 28 is functionallyoperative. The relief valve I3I serves to take care of the increase influid d splacement through the pipe line or channel 82 during the rapidmovement of the piston 90. This valve I3I is so designed as topositively prevent leakage during the feeding cycle, and serves as aneffective means for eliminating introduction of air in the fluid circuitduring the feeding stroke of the piston.

In Figure 3 'I have disclosed a modified arrangement whereby thedisplacement of a gear pump 58a may be varied without chang ng its speedof operation. The gear pump 58a disclosed in Figure 3 is similar to thevariable displacement gear pump disclosed in my co-pending application,Serial No. 430,868, filed February 24, 1930, which has since maturedinto Patent No.

1,912,737, and hence a detailed description thereof is not necessary fora clear understanding of the present invention. This pump includes apair of gears I32 and I34. The gear I34 is provided with radial ports orpassages i3Ii which com municate at their inner extremities with a portI38 of an osciliatory valve member I40. When the valve member I40occupies the position shown in Figure 3, the pump will be operating atits minimum degree of displacement, inasmuch as a portion of the fluidfrom the discharge chamber I42 is returned through the radial ports I36and the valve port I38 to the intake chamber I44.

However, if the valvemember I40 is moved in a counter-clockwisedirection so as to prevent any return flow of fluid from the dischargeor high pressure side of the pump to the lower pressure or intake side,said pump will operate at its maximum displacement. The shifting of thevalve I40 may be controlled by a hydraulic actuator Ia which correspondswith the hydraulic actuator shown in Figure 2. This actuator includes acylinder I02a and a piston I04a reciprocable therein, which is connectedby means of a piston rod I060. with an arm I46. This arm I46 isconnected with the valve I40 as clearly shown in Figure 3. The actuatorcylinder I02a is connected with the valve 54 in the same manner as thecylinder I02 is connected with said valve in Figure 1, namely, by thepipe lines I20 and lil. It will be apparent that when the main controlvalve 68 occupies the neutral position shown in Figures 1 and 3, thepiston i04a will be maintained in theposition shown in Figure 3 so as toposition the valvev I40 for minimum fluid displacement. It will also beapparent that when the valve member 68 is shifted to the left or to theright the piston I04a will be shifted to the right so as to conditionthe valve I4t for maxi- 90, and the movement of the actuator and slidecauses movement of a dog supporting slide I54 through the agency ofsuitable gearing. Thus, the slide acting through a rack I56, a geari,58, bevel gears 60 and E62, shaft I63, and a gear I64 which mesheswith a rack I66 on the underside of the dog supporting slide I54, causesmovement to he imparted to the latter. Dogs I68 and I cooperate withcompanion fingers I12 and I14 in causing the automatic shifting of themain valve 68 from central or neutral position to rapid approachposition, etc. Another dog I16 is adapted to engage the lever I22 whenthe actuator piston 90 or the supporting member I52 actuated therebyreaches the limit of its advance movement. With the foregoingarrangement, any desired cycle of operation can be obtained.

From the foregoing it will be clear that my invention contemplates theprovision of a very simple control arrangement for hydraulic circuitswherein it is desirabie to actuate the high displacement pump or gearpump at a minimum speed when said pump is not being employed for rapidtraverse purposes, and to automatically effect an increase in the speedof said pump when it is to be used for rapid traverse purposes. Thetwo-speed motor referred to in the description may be of anyconventional design, and, in fact,

all of the electrical equipment necessary to control the variation inspeed thereof may also beat well known design. By reducing the speed ofthe motor not only is power conserved, but the development-of heat inthe fluid medium, which has been experienced heretofore in operatingconventional gear pumps at continuous maximum speed over an extendedperiod ofv time, is materially reduced. This is of the utmost importancein connection with the operation of metal working machines in the shop,which must be used continuously through a working day and must sometimesbe operated continuously for a much longer period. Under such conditionsthe controlling of the speed of the gear pump, as set forth in mypresent invention, enables machines to he operated continuously over anextended period of time without experiencing increase in temperature ofthe fluid medium to any appreciable extent. The modified arrangementdisclosed in Figure 3: precludes the necessity of varying the speed of.the pump and only requires the displacement thereof to be varied inaccordancewith the conditions in the fluid circuit. The improved type ofgear pump disclosed in Figure 3 is particularly adapted for continuoushigh speed operation inasmuch as the provision of the radial ports andthe valve cooperating therewith positively prevents fluid from beingtrapped between the meshing gear teeth, and also prevents fluid slippagefrom the high to the low pressure side of the pump during thefunctioning thereof at high speeds. For a more detailed description of.the functional characteristics of said pump, reference is again made tomy above mentioned copending application which has since matured intoPatent No. 1,912,737.

In the foregoing description I have set forth that the gear pump isadapted to idle at its slower speed and to serve as a fluid propellingmechanism for driving the actuator piston 90 when the speed ordisplacement of the pump is increased. Obvionsly the invention is notlimited to this construction inasmuch as the pump may serve in certaininstances when it is operating at its slower speed as a fluidjpropellingmechanism for delivering fluid at a very low pressure to a shiftablepart, such as an actuator piston, and when operating at its increasedspeed or increased displacement, to drive said actuator piston at anincreased speed. In other words, my invention. contemplates theprovision of. a hydraulic system of control wherein the low pressurefluid propelling means or gear pump may function at low displacement forpropelling an actuator at a slower speed and at higher displacement forpropelling said actuator at increased speed. This arrangement isparticularly adapted for use in instances where a very slow movement isto be imparted to the tools of a machine during the setting upoperation, and a rapid movement after the set-up has been completed. Itwill therefore be apparent that my invention has a very broadapplication in the machine tool and other arts where it is desirable toactuate machine elements and the like at various speeds from a singlesource of fluid supply, said speeds being automatically controlled intimed relation with the shifting of the machine parts.

Obviously other modifications and changes may be made for controllingthe speed or variation in displacement of the gear pump withoutdeparting from the spirit of my present invention, said invention beinglimited only by the scope of the appended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

-1. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, a feed pump for imparting feedingmovement to said actuator, a low pressure independently operable highdisplacement pumping mechanism adapted to deliver fluid at various ratesfor imparting rapid traverse to said actuator, a valve for controllingcommunication between said pumping mechanism and said actuator, drivingmeans for said pumping mechanism, and means operable in timed relationwith the actuation of said valve for controlling the rate of delivery ofsaid pumping mechanism.

2. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, a feed pump for imparting feedingmovement to said actuator, a low pressure independently operable highdisplacement pumping mechanism adapted to deliver fluid at various ratesfor imparting rapid traverse to said actuator, a valve for controllingcommunication between said pumping mechanism and said actuator, drivingmeans for said pumping mechanism, and pressure actuated means operablein timed relation with the actuation of said valve for controlling therate of delivery of said pumping mechanism.

. 3. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, a pumping mechanism adapted todeliver fluid at various rates for imparting rapid traverse to saidactuator, a valve for controlling the fluid flow between 'said pumpingmechanism and said actuator to govern the direction of travel thereof,driving means for said pumping mechanism, and means hydraulicallycoupled with said valve and operable in response to the pressure of saidcontrolled fluid for controlling the rate of delivery of said pumpingmechanism.

4. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a. low pressure highdisplacement pumping mechanism adapted to deliver fluid at various ratesand for imparting rapid traverse to said actuator at maximum delivery, avalve for controlling the fluid flow between said pumping mechanism andsaid actuator, driving means for said pumping mechanism, control meansoperable in accordance with a pressure condition within the valve toeffect a decrease in fluid delivery, said pressure condition beingcaused by shifting said valve to a position in which it disconnects saidpumping mechanism from said actuator, and a second pumping means adaptedto deliver fluid to said actuator when said valve is positioned todisconnect said first pumping means from said actuator.

5. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a low pressure high displacementpumping mechanism adapted to deliver fluid at various rates forimparting rapid traverse to said actuator at maximum delivery, a valvefor controlling the fluid flow between said pumping mechanism and saidactuator, driving means.for said pumping mechanism, control means forsaid pumping mechanism operable when the valve establishes the fluidflow between said pumping mechanism and said hydraulic actuator toeffect an increase in displacement of said pumping mechanism andoperable in accordance with a pressure condition of said controlledfluid to effect a decrease in fluid delivery, said pressure conditionbeing caused by shifting said valve to a position in which itdisconnects said pumping mechanism from said actuator, and a secondpumping means adapted to deliver fluid to said actuator when said valveis positioned to disconnect said first pumping means from said actuator.

6. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a low pressure high displacementpumping mechanism for imparting rapid traverse to said actuator atmaximum delivery, a valve for controlling the fluid flow between saidpumping mechanism and said actuator, a ariable speed electric motor fordriving said pumping mechanism, and control means operable when thevalve occupies a given position to effect an increase in the speed ofsaid motor and operable in' accordance with a pressure condition of saidcontrolled fluid to effect a decrease in fluid delivery, said pressurecondition being caused by shifting said valve to a position in which itdisconnects said pumping mechanism from said actuator.

7. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a relatively large capacitypumping mechanism for imparting rapid traverse to said actuator atmaximum delivery, a valve for controlling the fluid-flow between saidpumping mechanism and said actuator, driving means for said pumpingmechanism, and means operable in instantaneous timed relation withtheactuation of said valve and in accordance with a pressure condition ofsaid controlled fluid for varying the rate of delivery of fluid fromsaid large capacity pumping mechanism to said actuator, said pressurecondition being caused by shifting said valve to a position in which itdisconnects said pumping mechanism from said actuator.

8. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a low pressure high displacementpumping mechanism for imparting rapid traverse to said actuator. atmaximum delivery, said pumping mechanism including a valve shiftable forvarying the displacement thereof, a second valve for contemporaneouslycontrolling the opening and closing of. communication of said pumpingmechanism with both the intake and discharge sides of said actuator,driving means for said pumping mechanism, and means shiftable in timedrelation with the actuation of said second valve' for controlling theshifting of the flrst valve and thereby effecting a variation indisplacement of said pumping mechanism.

9. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a gear pump for imparting rapidtraverse to said actuator at various rates, a valve for controlling thefluid flow between said gear pump and said actuator to govern thedirection of movement of said actuator, driving means for said pump, andcontrol means operable upon the shifting of said valve and in accordancewith a pressure condition of said controlled fluid for controlling therate ofidelivery of said gear pump, said pressure condition being causedby shifting said valve to a position in which it disconnects said gearpump from said actuator.

10. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a variable delivery gear pumpfor imparting rapid traverse to said actuator at maximum delivery, avalve for controlling the fluid flow between said gear pump and saidactuator to govern the direction of movement of said actuator, drivingmeans for said pump, and control means operable upon the shifting ofsaid valve and in accordance with a pressure condition of saidcontrolled fluid for varying the rate of delivery of said gear pump,said pressure condition being caused by shifting said valve to aposition in which it disconnects said pumping mechanism from saidactuator.

11. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, said actuator including a cylinderhaving a piston therein, pumping means for propelling said actuator at afeeding rate, low pressure pumping means for propelling said actuator ata rapid rate, said low pressure pumping means being adapted to deliverfluid at various rates, one of said pumping means being operableindependently of the other for effecting the relative propulsion of saidpiston and cylinder, and means operable in timed relation with respectto the shifting of said actuator for varying the rate of delivery of thelow pressure pumping means.

12. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, said actuator including a cylinderhaving a piston therein, pumping means for propelling said actuator at afeeding rate, low pressure pumping means for propelling said actuator ata rapid rate, one of said pumping means being operable independently ofthe other'for effecting the propulsion of said actuator, and

means for decreasing the displacement of the low pressure pumping meansduring the operative functioning of the other pumping means and forincreasing the displacement of said low pressure pumping means when theother pumping means is functionally inoperative.

13. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, said actuator including a cylinderhaving a piston therein, pumping means for propelling said actuator at afeeding rate, low pressure pumping means for propelling said aptuator ata rapid rate, one of said pumping means being operable independently ofthe other for effecting the propulsion of said actuator, means fordecreasing the displacement of the low pressure pumping means during the0perative functioning of the other pumping means and for increasing thedisplacement of said low pressure pumping means when the other pumpingmeans is functionally inoperative, and a valve mechanism for controllingthe delivery of fluid from said low pressure pumping means to saidactuator.

14. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, said actuator including acylinder having a piston therein, pumping means for propelling saidactuator at a feeding rate, pumping means for propelling said actuatorat a rapid rate, said first pumping means being functionally operablefor propelling purposes independently of said second pumping means, afluid reservoir directly connected with the intake of said secondpumping means, a valve for controlling the fluid delivered by saidsecond pumping means from said reservoir and for controlling the returnof fluid to said reservoir, and a relief mechanism operable forpermitting the return of fluid therethrough to the reservoir, said fluidbeing returned from the discharge side of said actuator at pressuresdeveloped in the return S of the system when the second pumping means isoperatively functioning to receive fluid from said reservoir and deliversaid fluid for propelling purposes to said actuator.

15. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, said actuator including a cylinderhaving a piston therein, pumping means for propelling said actuator at afeeding rate, pumping means for propelling said actuator at a rapidrate, a fluid reservoir directly connected with the intake of saidsecond pumping means, a valve for controlling the fluid delivered bysaid second pumping means from said reservoir and for controlling thereturn of fluid to said reservoir, and a relief mechanism for permittingthe return of fluid therethrough to the reservoir, said relief mechanismbeing non-responsive to pressures developed in the return side of thesystem during the operative functioning of the first pumping means, andresponsive to pressures developed in the return side of the system whensaid second pumping means receives fluid from said reservoir anddelivers said fluid for propelling purposes to said actuator.

. 16. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, said actuator including a cylinderhaving a piston therein, a plunger pump for propelling said actuator ata feeding rate, a second pump for propelling said actuator at a rapidrate, a fluid reservoir for supplying fluid directly to the intake sideof said second pump, a shiftable control 'valve to govern theindependent delivery of fluid from said pumps to said actuator, achannel for conducting return fluid from said valve to said reservoir,and a relief valve connected with said channel, said relief valve beingfunctionally operative to permit the flow of fluid therethrough intosaid reservoir when said second pump receives fluid from said reservoirand delivers said fluid to said actuator and adapted to prevent saidflow of fluid therethrough during the operative functioning of saidplunger pump.

17. A hydraulicactuator system including a hydraulic actuator forshifting machine parts and the like, a feed pump for propelling saidactuator at a feeding rate, a rapid traverse variable delivery pump, avalve mechanism for controlling delivery of fluid between said pumps andsaid actuator, and means operable in timed rela-' tion with theactuation of said valve for controlling the rate of delivery of saidrapid traverse pump.

18. A hydraulic actuator system including a hydraulic actuator forshifting supporting parts and the like, a feed pump for propelling saidactuator at afeeding rate, a rapid traverse pump adapted to deliverfluid at various rates and driven independently of said feed pump, avalve mechanism for controlling delivery of fluid between said pumps andsaid actuator, a variable speed drive for said rapid traverse pump, andmeans for controlling said drive to vary the delivery of the pump inaccordance with the fluid capacity requirements of the system.

19. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, a relatively large capacity pumpingmechanism for imparting rapid traverse to said actuator, a valve forcontrolling delivery of fluid between said pumping mechanism and saidactuator and for governing the direction of travel of said actuator, anda second valve for automatically causing a decrease in the rate of fluiddelivery to the actuator at a predetermined interval in the cycle ofoperation of said-actuator.

20. A hydraulic actuator system including a hydraulic actuator forshifting machine parts and the like, a relatively large capacity pumpingmechanism for imparting rapid traverse to said actuator, a valve forcontrolling delivery of fluid between said pumping mechanism and saidactuator and for governing the direction of travel of said actuator, anda second valve means which is adapted in one shifted position to enablefluid to be delivered to the actuator at a given rate and in anotherposition to automatically efiect a variation in the rate of fluiddelivery to said actuator at a predetermined interval in the cycle of Voperation of said actuator.

;-21'.'Ahydrau1ic actuator system including a hydraulic actuator forshifting machine parts and the like, a relativelylarge capacity pumpingmechanism for imparting rapid traverse to said actuator, a valve forcontrolling delivery of fluid between said pumping mechanism and saidactuator and for governing the direction of travel of said actuator, anda second valve means which is operable in timed relation with theactuation of the first valve and adapted in one shifted position toenable fluid to be delivered to the actuator at a given rate and inanother position to effect a variation in the rate of fluid delivery tosaid actuator.

- ERNEST J. SVENSON.

